Telematics Chapter 6: Network Layer - Freie Universität Berlin
Telematics Chapter 6: Network Layer - Freie Universität Berlin
Telematics Chapter 6: Network Layer - Freie Universität Berlin
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ICMP: Header<br />
● ICMP message fields<br />
● Type: purpose of the ICMP message<br />
● Around 40 defined ICMP message types<br />
● Types 41 – 255 for future use<br />
● Code: additional information about<br />
the condition<br />
● Very rarely used<br />
● Checksum: same type of checksum as<br />
used for IP<br />
● Message categories<br />
● Error messages: to report an event.<br />
These messages do not have a<br />
response.<br />
● Error messages include the IP header<br />
that generated the error!<br />
● Queries: To get some information<br />
from a node. These messages have a<br />
matching response.<br />
1 byte 1 byte 2 byte<br />
Univ.-Prof. Dr.-Ing. Jochen H. Schiller ▪ cst.mi.fu-berlin.de ▪ <strong>Telematics</strong> ▪ <strong>Chapter</strong> 6: <strong>Network</strong> <strong>Layer</strong><br />
Type Code Checksum<br />
ICMP Data<br />
(content and format depends on Type)<br />
General format of ICMP messages<br />
1 byte 1 byte 2 byte<br />
Type =3 Code Checksum<br />
Unused (all 0 bits)<br />
IP Header (20 bytes)<br />
and<br />
First 8 bytes of original packet data<br />
Format of Destination Unreachable ICMP message<br />
6.113
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